Mechanical arm



FIG. 1 is a first perspective view of a mechanical arm showing the claimed design in accordance with the present disclosure;

FIG. 2 is a second perspective view thereof;

FIG. 3 is a third perspective view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a left side elevational view thereof;

FIG. 7 is a right side elevational view thereof;

FIG. 8 is a top plan view thereof; and,

FIG. 9 is a bottom plan view thereof.

The broken lines in the Figures are for the purpose of illustrating portions of the article that: form no part of the claimed design. 

CLAIM The ornamental design for a mechanical arm, as shown and described. 